The vast economic importance of the hydrocracking process in modern petroleum refineries has resulted in significant development work aimed at improving the performance of hydrocracking process units. This development has resulted in the development of high activity zeolitic catalysts for use in these units. This high activity gradually decreases during the operation of the process unit due to the accumulation of carbonaceous deposits on the catalyst and through other means of deactivation. The initial high activity of fresh catalyst or newly regenerated catalyst has been recognized as a cause of operational or performance problems. The art has therefore developed methods of reducing the initial activity of fresh or newly regenerated hydrocracking catalyst through the addition of selective catalyst inhibitors. Many of these inhibitors contain nitrogen with ammonia being a preferred form of the selective catalyst inhibitors.
Many processes ammoniate the high zeolite hydrocracking catalyst via a high pressure injection of anhydrous ammonia. Such an injection process involves designing a high pressure injection system including a metering pump, high pressure piping, and instrumentation. There are mechanical as well as safety issues associated with the maintenance of the high pressure metering pump. Additionally, there is also the probability of ammonia leakage at high pressure. Alternatively, a refiner may contract for the supply of bulk ammonia with a supplier and require supplier to provide the pumping equipment. However, this can present issues due to reliability of the pumping systems. Additionally, the safety of the handling and pumping at high pressure anhydrous ammonia would still exist.
Instead of anhydrous ammonia, it is also known to use aqueous ammonia by, for example, injecting the aqueous ammonia into the recycle vapor line associated with a hydrocracking reactor. While such a process will alleviate some of the safety and handling concerns associated with high pressure anhydrous ammonia, the aqueous ammonia is still being used in a high pressure system. This requires the high pressure piping and pumping previously mentioned and includes the safety concerns discussed above.
It would be desirable to have a process that provides the safety benefits of the aqueous ammonia without using a high pressure injection system and equipment.